i think zonatandem's comments make good sense. many people mistakenly believe they will be more comfortable with a very upright position, and for short rides this works. but if you spend alot of time on your bike you need to be in a postions which spreads the load out over your hands and back and shoulder and butt. too upright and eventually your butt cannot take all the weight. by extending your handlebars away and down you will allow your body to choose different areas to take the weight. also changing the postions of your hand on the bars helps. but the best way to take the weight off your butt is to pedal really hard with your legs, which takes the weight off your butt.
bob